The invention relates to a cryopump comprising an exterior housing having an interior space formed therein. A refrigerator is at least partially located within the interior space for operating the cryopump. The refrigerator has at least one pumping surface located within the interior space. A heating element is attached to the pumping surface for heating the pumping surface. An inlet valve is attached to the housing and opens into the interior space. A backing pump is operatively connected to the interior space.
A cryopump operated with a cold source or a refrigerator is known from, for example, DE-OS 2,620,880. Pumps of this type conventionally have three pumping surface regions designated for the agglomeration of different types of gases. The first surface region is in thermally well-conductive contact with the first stage of the refrigerator and, depending on the type and capacity of the refrigerator, has an essentially constant temperature between 60 and 100 K. Conventionally, a radiation shield and a baffle are part of these surface regions. These components protect the pumping surfaces with lower temperatures against incident thermal radiation. The pumping surfaces of the first stage preferably serve in the agglomeration of gases that condense relatively simply, such as water vapor and carbon dioxide, by means of cryocondensation.
The second pumping surface region is in thermally-conductive contact with the second phase of the refrigerator. During pump operation, this stage has a temperature of approximately 20 K. The second surface region preferably serves to remove gases that can only be condensed at lower temperatures, such as nitrogen, argon or the like, likewise by means of cryocondensation.
The third pumping surface region likewise shares the temperature of the second stage of the refrigerator (correspondingly lower in a refrigerator having three stages), and is coated with an adsorption material. On these pumping surfaces, essentially the cryoadsorption of light gases, such as hydrogen, helium or the like, is intended to take place.
For regeneration of a cryopump, it is necessary to heat the pumping surfaces. This can take place by means of radiation, or with the aid of heated regenerative gases, which flow through the housing of the cryopump. A further possibility (see DE-OS 3,512,614) is to equip the pumping surfaces with electrical heating devices and put these into operation during the regeneration process. With the heating devices, when the backing pump connected to the interior of the pump is running, the pumping surfaces are heated to, for example, 70.degree. C. until the backing pressure (approx. 10.sup.-2 mbar) is again reached after the precipitated gases are removed. A total regeneration of the pumps in accordance with these methods lasts for several hours, since the regeneration duration is a combination of the actual regeneration time and the time required for putting the pump back into operation, particularly for cold operation of the pumping surfaces.
Cryopumps are frequently used in semiconductor production technology. In many applications of this type, gases predominantly arise that only charge the pumping surfaces of the second stage. It is therefore known (see DE-OS 3,512,614) to execute regeneration only of the low-temperature pumping surfaces. This occurs by means of separate heating of the pumping surfaces of the second stage.
In all regeneration processes, the inlet valve, which is typically disposed upstream of the inlet opening of the cryopump, must be closed, that is, pump operation and hence production operation must be interrupted.